This invention relates to collapsible metal trusses and more particularly to a truss which can be erected in a number of different sizes and configurations and which, prior to erection and assembly, comprises at least two jackknifed sections which can be conveniently boxed in a folded state for shipment.
Roof trusses for commercial and residential buildings are typically prefabricated using wooden beams and metal joiner plates. Such prefabricated structures are large and heavy and must be shipped from the factory to the building site in small numbers on a large truck.
The prior art shows efforts to design collapsible building trusses made of metal components which can be telescoped and folded so as to reduce the size and, presumably, the weight of the structure to be shipped to the building site. An example is shown in Mueller et. al. U.S. Pat. No. 3,760,550 issued Sep. 25, 1973, The metal truss structure disclosed in this United States Patent can be collapsed to a shipping length of 28 feet and, according to the patent, can be erected at the building site into a roof truss having a predetermined pitch.
The present invention provides a collapsible metal building truss made up of a number of preassembled jackknife sections which are easily and conveniently shipped in a folded state and which can be opened and assembled at the building site to create a truss of nearly any desired configuration and size; i.e., the resulting truss can be symmetrical or asymmetrical, of any desired width within a predetermined range, of any desired height within a predetermined range, and of any desired pitch consistent with the selected height and width. In a specific embodiment hereinafter disclosed, the truss can also be erected in both flat and cathedral ceiling configurations.
Because the truss of the present invention is made up of preassembled and jackknife folded sections, the boxed and shipped size is far smaller than that of the Mueller et. al. truss. This shipping size advantage, in combination with the size and configuration flexibility described above, is believed to represent a substantial advance in the collapsible truss art.
As hereinafter described with reference to two specific but illustrative embodiments, the jackknife sections are made up of partial chords and partial webs, the chords typically having U-shaped cross sections and the webs typically having H-shaped cross sections. The sizes of the chord sections vary between layer xe2x80x9couterxe2x80x9d sections and slightly smaller xe2x80x9cinnerxe2x80x9d sections. The web sections are sized to fit within the chord sections. The cross-sections of the chords are preferably U-shaped while the web sections are preferably H-shaped.